Sixty-five million years ago, the dinosaurs disappeared in what’s known as the Earth’s fifth mass extinction. Today, a sixth mass extinction could be well underway and humans are the likely culprit, according to new research published in Science Advances.

The past five mass extinctions on Earth were caused by large-scale natural disasters like meteors or enormous chains of volcanic eruptions, wiping out between half and 96 percent of all living species.

But the modern mass extinction isn’t being caused by a freak act of nature, the researchers say. It’s being caused by man-made changes to the environment including deforestation, poaching, over-fishing and global-warming, and it’s proving to be just as deadly.

Recently, species like the Emperor Rat, the Desert Rat Kangaroo, the Yangtze River Dolphin, the Skunk Frog and the Chinese Paddlefish, amongst hundreds of others, are believed to have become extinct.